Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Consolidated Balance Sheets
Allowance for doubtful accounts	$ 648	$ 851
Estimated allowance for refunds and appeals	$ 35,518	$ 41,020
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	600,000,000	600,000,000
Common stock, shares issued	91,845,947	90,748,740
Common stock, shares outstanding	91,838,470	90,741,340
Treasury stock, shares	7,477	7,400